Paper Authors

Grant Richards
Purdue University

Grant Richards is a doctoral candidate in the College of Technology at Purdue University. He currently serves as a graduate instructor in the Electrical and Computer Engineering Technology department. His research interests include pedagogy supporting math\physics constructs, visualization tools and RF electronics.

John Denton
Purdue University

John Denton is an Associate Professor in Electrical and Computer Engineering Technology in the Purdue University, College of Technology in West Lafayette, Indiana. He received his Ph.D. in Electrical Engineering from Purdue University in 1995. His areas of interest and expertise are analog electronics, RF electronics and electronic materials. He is the author or co-author of over 50 journal articles and conference proceedings.

Abstract

NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

A Laboratory Experience in Impedance Matching using
Transmission Line Stubs

Abstract
Impedance matching is a fundamental concept of RF circuit design. The proper application of
impedance matching circuits allows for maximum power transfer between devices with
minimum reflection of input signals. This concept is traditionally presented in mathematical
form in conjunction with a Smith chart presentation. This paper presents a laboratory approach
which uses these traditional forms of presentation in conjunction with real-time visualizations
and low cost hardware demonstrations to present impedance matching concepts in multiple
forms to address a range of student learning styles.

This paper details a successful laboratory experience focused on presenting impedance matching
concepts at frequencies near 100 MHz through the design, simulation and measurement of a stub
matching network. The procedures include hand and Smith Chart calculations reinforced using
Applied Wave Research's Microwave Office to provide interactive simulations of the network.
The designs and simulation results are then verified through the construction and measurement
of the impedance matching system on a spectrum or network analyzer.

The laboratory exercises are designed to be performed in two hours. The exercises have been
completed by 64 undergraduate students working in pairs over a period of two years with a
completion rate over 90%. The laboratory presents concepts in multiple presentation forms to
accommodate a range of student learning styles. This paper presents procedures, student
perspectives and performance results on this laboratory experience.

Introduction

The concept of impedance matching has historically been poorly understood by students in our
program. While students are often able to follow an algorithmic approach which ultimately leads
to a numerical solution, in the end they are routinely unaware of the role and contributions of
each component in the matching network. This inability to relate mathematical expressions to
the physical components in a network propagates through to later topics and courses which
explore more advanced RF filter applications which commonly interchange between
transmission lines and discrete inductances and capacitances. The purpose of this laboratory
experience is to reinforce the relationship between the mathematics used in the design of single
stub impedance matching networks and the physical components in the network. This is
supported with the addition of interactive simulations using Microwave Office to complement
existing mathematical and hardware presentations.

Background

This laboratory is designed to be completed in a two-hour laboratory session for those
successfully completing pre-laboratory exercises. While a number of RF simulation packages
may be used to perform the listed simulations, the real-time tuning capabilities of Microwave
Office provide for a high degree of interactivity which is a primary component of this